In message , at 13:00:34 on
Fri, 13 May 2011, Basil Jet remarked:
If the lift had doors on two sides and sensors to detect people
within, a single lift could link the street, the ticket hall and the
platforms without compromising the barrier line.

With doors opening alternate sides I suppose.

The lift would have two modes, streetside and airside, and could only
switch between the two when empty. On the ticket hall level the mode
would control which of the two doors opened.

And I predict it would spend most of its time full of people wanting the
opposite mode to that which it was currently performing, and refusing to
get out.
--
Roland Perry